A recent trend in wireless communications is to move away from handheld devices exclusively to wireless devices that are wearable, that is, either part of or attached to garments, or worn as an appendage on the body such as with watches, bracelets, anklets, necklaces, earrings, and so on.
The challenge in these new wearable wireless devices is twofold. Firstly, their proximity to the body requires antennas that are wideband and or not sensitive to the tuning to accomplish the wireless communications. Secondly, these wearable devices must have antennas that are very small physically, yet are wideband or work over multiple bands over a wide frequency spectrum. The problem becomes acute, when considering the wavelengths used by these wireless devices, which typically range from roughly 40 cm to 5 cm, while the devices themselves, in contrast, are dramatically small compared to wavelength. Thus the antennas are very electrically small, and have difficulty operating over a wideband or multiple bands over a wide spectrum. Further, such prior art antennas have not been able to perform well in an environment where there is substantial near-field interaction with the associated RF electronics and also the user's body.
Prior art is manifested by a variety of notched antenna structures resembling inverted-F antennas or dipoles. While these antennas tend to work well on portable devices such as handsets, they are roughly a factor of 30-50% too big to fit within miniature communications devices or be a small part of an attachment to an appendage, e.g., a watch, pendant, necklace, small portion of a worn garment, and the like. The prior art may attempt to solve this by having small, individual antennas that operate at Wi-Fi or Bluetooth frequency bands, for example, but do not encompass a wide enough swath of frequency bands such as seen with modern cell phone enabled devices. Furthermore, diversity needs are not met by limited number of band antennas nor larger portable band antennas.
There is a need then for an antenna that is attached to one or more body appendage(s) or is part of a miniature communications device(s) attached to an appendage(s).